SALTER — A CHRISTMAS LECTURE ON COAL. 



9 



remainder is hid beneath the sea. But even that half will show the 

 beds in the same order or succession. The Mountain Limestone is 

 a fine rock, and forms most of the high moory ground on the west. 

 Many a border skirmish has been fought upon the heather that 



Fig. 1. — Ideal Section of a Coal Basin, to show the usual arrangement of the Beds, and the 

 Dislocations caused by Faults. 



a, Old Red Sandstone ; b, Carboniferous or Motvntain Limestone ; c, Millstone Grit ; d, Fare- 

 well Rock, sandstone chiefly ; e, f, g, h, coal seams, or beds, the layers of coal from one foot 

 to ten feet thick, and with shafts piercing two, three, or more of the beds, as the case may 

 be ; i, Magnesian Limestone and Red Sandstone, unconformable on the Coal-beds. 



covers its surface ; and many a bold moss-trooper has ridden for dear 

 life across the bogs that ornament this formation,* and the one suc- 

 ceeding, viz., Millstone Grit. 



It should be noticed that the "Millstone Grit" is all or nearly all 

 sandstone— sometimes clayey, but more often hard; and the lower 

 part of the coal-formation itself is nearly all sandstone, with a few 

 bands of clay or shale. But as we rise higher in the beds, the clay 

 grows more and more, the sandstone still being present in large 

 quantity, till shale, as it is called, often makes up the chief part of 

 the beds. Under every seam of coal, with scarcely an exception, lies 

 a bed of what is called fire-clay, a rather hard clay, which makes 

 excellent linings for stoves and furnaces, and which besides is used 

 for crucibles and other purposes. Of this clay more by-and-bye, 

 when we come to speak of how coal is formed. 



c ^ c c c c c c 



Fig. 2. — Ideal Section showing Granite and Killas (soft slate), with Metalliferous Veins. 

 *, granite ; a, killas ; e, c, c, metal veins. 



And now it will be seen from our diagram, and from what has 



VOL, IV. 



* " He rode a small but hardy nag, 



That o'er a bog — from hag to hag — 

 Could bound like any Bilhope stag." 



B 



